The present invention relates to hermetic scroll compressors and particularly to discharge check valves therefor which are intended to prevent reverse rotation, or reverse orbiting motion, of the orbiting scroll member.
Hermetic scroll compressors generally include a sealed housing in which are disposed a compression mechanism and an electric motor having a stator and a rotor, the rotor being operatively coupled, through a shaft, to drive the somewhat planar orbiting scroll member of the compression mechanism. The orbiting scroll member is provided with a spiral or involute wrap extending from one side thereof, that wrap interleaved with a mating wrap which extends from the interfacing side of a somewhat planar fixed scroll member. The compression mechanism is provided with means, such as an Oldham coupling, to prevent rotation of the orbiting scroll member with the rotor. Refrigerant gas at substantially suction pressure is normally introduced into the compression space between the interleaved scroll wraps at a location near the radially outer edge of the fixed scroll member, and is compressed in crescent-shaped pockets or compression chambers partially defined by the interleaved scroll wraps as the orbiting scroll moves. The gas exits from between the scroll members at substantially discharge pressure through a discharge port provided near the radial center of, usually, the fixed scroll member. The discharge pressure gas is normally exhausted from the discharge port into a discharge pressure gas space defined by at least a portion of the compressor housing. Examples of prior scroll compressors are disclosed in U.S. Pat. Nos. 6,086,342, issued Jul. 11, 2000, U.S. Pat. No. 5,496,160, issued Mar. 5, 1996, U.S. Pat. No. 5,306,126, issued Apr. 26, 1994, and U.S. Pat. No. 6,139,294, issued Oct. 31, 2000, each of which is assigned to the assignee of the present application and expressly incorporated herein by reference.
One problem associated with prior scroll compressors relates to their being induced into reverse rotation or orbiting upon shutdown of the compressor as compressed refrigerant within the discharge pressure gas space expands and reversely flows back through the discharge port in the fixed scroll member. As the discharge pressure gas expands and backflows from the discharge pressure gas space into the compression space between the interleaved scroll wraps, the orbiting scroll is caused to orbit in the direction opposite that in which the gases were initially compressed. Thus, on shut down, the compressor may behave like an expansion motor, the compressed gases causing rotation of the driveshaft in a direction opposite that in which the electric motor normally drives the shaft. Moreover, in some scroll compressors, during periods of brief power interruption during which the compressor is caused to be reversely rotated by expanding discharge gases, the compressor may continue rotation in the reverse direction, driven by the motor, if power is restored to the motor while the compressor is still reversely rotating under influence of the expanding discharge gases. In such situations, the compressor may run in the reverse direction for quite some time. Objectionable noise and vibration usually accompany such reverse movement of the orbiting scroll, and if prolonged, such reverse movement may result in damage to the compressor.
Reverse rotation or orbiting in scroll compressors is a well known problem, and much effort has been made to preclude it. Previous scroll compressors have been provided with discharge check valves of various types provided over the discharge port to prevent reversely flowing discharge gases from reentering the space between the interleaved scroll wraps. These previous discharge check valves, however, often rely on the backflowing discharge gas to close them, which may slow their reaction time and lessen their reliability. Further, previous discharge check valves often require closely toleranced machining, or expensive tooling, and may include a multitude of component parts, which may result in high capitalized costs or substantial amounts of labor. Moreover, some prior discharge check valves are positioned such that, when open, they significantly block and undesirably restrict the outflow of gas from the discharge port. It is therefore desirable to provide a discharge check valve assembly for preventing reverse rotation or orbiting in a scroll compressor, which is both more reliable and less expensive than those previously known, and which does not significantly block or undesirably restrict the flow of gas from the compression mechanism.
The present invention addresses the shortcomings of previous compressor discharge check valve assemblies, and provides the above-mentioned desired advantages thereover.
The present invention provides a compressor assembly including a housing, a compression mechanism disposed in the housing and having a discharge port, and a discharge check valve assembly. Gas substantially at suction pressure is received into the compression mechanism, compressed and discharged substantially at discharge pressure from the compression mechanism through the discharge port. The discharge check valve assembly has at least one elongate guide pin extending from the compression mechanism and a valve plate disposed about the guide pin. The valve plate has a closed position at a first position along the guide pin in which the valve plate covers the discharge port and an open position at a second position different than the first position along the guide pin in which the valve plate does not cover the discharge port. Gas substantially at discharge pressure and having been discharged from the compression mechanism is substantially prevented by the valve, in its closed position, from reentering the discharge port.
The present invention also provides a compressor assembly including a housing, a compression mechanism disposed in the housing and having a discharge port, and a discharge check valve. Gas substantially at suction pressure is received into the compression mechanism, compressed and discharged substantially at discharge pressure from the compression mechanism through the discharge port. The discharge check valve assembly includes an elongate guide pin connected to the compression mechanism and having a longitudinal axis and a valve plate through which the guide pin extends and which substantially lies in a plane which is not parallel with the guide pin longitudinal axis. The discharge check valve assembly also includes means for limiting movement of the valve plate between a closed position in which the valve plate covers the discharge port and the plane is substantially normal to the guide pin longitudinal axis, and an open position in which the valve plate does not cover the discharge port and the plane is inclined relative to the guide pin longitudinal axis.